Riverine food environments and food security: a case study of the Mekong River, Cambodia

Abstract Rivers are critical, but often overlooked, parts of food systems. They have multiple functions that support the food security, nutrition, health and livelihoods of the communities surrounding them. However, given current unsustainable food system practices, damming and climate change, the majority of the world’s largest rivers are increasingly susceptible to environmental degradation, with negative implications for the communities that rely on them. Here we describe the dynamism and multifaceted nature of rivers as food environments (i.e. the place within food systems where people obtain their food) and their role in securing food security including improved diets and overall health. We also provide a conceptual framework that explain rivers as food environments within the broader food system and describe approaches to characterizing these food environments to better inform our understanding of how they influence food security and nutrition outcomes. Applying this framework to the Mekong River in Cambodia, we describe rivers as multifaceted wild food environments embedded within ecosystems, sociocultural and political environments and sectors of influence. We also explain the ways in which individual factors might influence how communities interact with this food environment. Developing and articulating food-related, ecosystem-specific frameworks and their constructs can guide implementation of policies aimed to improve specific public health or environmental sustainability outcomes. Our conceptual framework incorporates the multiple dimensions of rivers, which will aid future work and public health policy framing to better describe, understand and intervene to ensure protection of rivers’ biodiversity and ecosystems as well as food security, health and livelihoods.


Introduction
Climate change affects food security and the nutritional well-being of populations worldwide. By 2050, an estimated 183 million additional people will be at risk of hunger linked directly to climate change. 1 In turn, current food systems, responsible for a third of total global greenhouse gas emissions, hasten climate change and degradation of ecosystems leading to significant deforestation and biodiversity loss. 2 Ecosystems are crucial components of our food system and serve as food environments, that is the interface at which consumers interact with the broader food system by making choices within a physical, economic, political and sociocultural context. 3 River ecosystems have historically provided numerous food-related benefits to humans including irrigation, livelihoods and as a vessel for food. Rivers can be described as nutrient highways across the earth's surface, transporting sediment and water, sequestering carbon from the atmosphere, and connecting and storing immense biodiversity through aquatic life. The flow and transportation of sediment create environments for cultivation (e.g. rice farming), with river deltas being one of the world's most agriculturally productive areas. 4 Rivers support approximately a third of all global food production, and an estimated 70% of freshwater from rivers is used for agriculture. 5, 6 In addition, in countries where consumption data is available, freshwater fish, primarily from inland fisheries, are estimated to be the primary animal source protein consumed by more than 119 million people. 7 Rivers are therefore integral to food systems and a critical resource for assuring nutritional wellbeing and food security. Their multidimensional nature gives them a unique position as a natural, wild food environment, a concept not well-characterized in the literature or in the public health policy sphere.
Emerging research focuses on the importance of food environments as a point of convergence between food, human beings, choice and acquisition. 8,9 Environmental, economic, and other shocks can affect food environments, which are dynamic spaces embedded in interdependent global food systems. Characterizations of food environments have primarily focused on the built food environment, such as supermarkets, corner stores and kiosks. The literature remains scant on depictions of informal and wild food environments (e.g. forests, rivers) as a source of food security despite the importance of these environments and communities' reliance on them, especially in low-and middle-income countries. 10 Livelihood and income-generating activities related to rivers are equally dynamic and include fishing, farming and trade. However, given the unsustainability of modern food systems and human activities coupled with climate change, 30 out of 47 of the world's largest rivers are under threat of human water insecurity and biodiversity loss ultimately linked to food productivity loss. 11 These unsustainable food systems have implications for food security, nutrition and health for river-dependent populations. While there is broad recognition of these connections, the role of rivers Riverine environments and food security, Cambodia Swetha Manohar et al.
as a crucial food environment in protecting against food insecurity and malnutrition is rarely described. This evidence gap can be conceivably attributed to the imbalance of research undertaken in high-versus lowresourced settings where urbanization and market-driven economies have given rise to primarily built food environments versus a more heterogenous food environment typology. 8,12 This paper will expand on the dynamism and multifaceted nature of rivers as food environments and their role in securing food security. By using the Mekong River in Cambodia as a case study, we will discuss how to understand rivers as food environments, how rivers underpin food security and their unique features and threats. Further, we offer two conceptual frameworks. The first allows for the conceptualization of rivers as a food environment, while the second establishes a structure to assess rivers as food environments and highlights existing assessments that can be applied. Both frameworks can be useful constructs in understanding how to develop and implement policies related to improving food security, diets and public health outcomes.

Rivers as a food environment
We adapted a schematic socioecological model of food environments 13 to posi-tion rivers as food environments within the broader food system and to reveal its broader ecosystem (Fig. 1). We selected this conceptual framework based on its grounding in the socioecological model and theory, in which most of the food environment literature is rooted. 14 The framework emphasizes the multilevel linkages that ultimately impact individuallevel dietary intake and nutrition, bringing to focus the interrelated nature between environments and people. Furthermore, this evidence-based framework situates its conceptual thinking in low-and middleincome country contexts and prominently features the wild food environment in addition to the built food environment. The framework advances our understanding by demonstrating how rivers are pivotal food environments through which food security and healthy diets are secured while also being shaped by and interacting with other factors. We have adapted the framework to reflect the entire river ecosystem and its constant interaction with the sociocultural and political environment, various sectors of influence, food environments and ultimately individual-level factors and diets. These interactions can be bidirectional, whereby shifts in sectors of influence such as riverbased livelihoods or unregulated market activity can shape food environments as much as consumer food preferences that are river-reliant can drive changes in river ecosystems.
We first considered the environmental and political aspects of rivers and food environment attributes more broadly when adapting the original framework. Next, we considered how the unique attributes of rivers lend themselves to function as food environments. Table 1 expands the conceptual framework by describing how factors included in each band in the model relate to riverine food environments. We generated Table 1 through an iterative approach where we assessed each factor for its applicability to riverine food environments using peer-reviewed literature and relying on the authors' collective interdisciplinary expertise. The river ecosystem band (Fig. 1) is informed by river ecology literature as it relates to food security. 15,16 The literature search was conducted with variations of the following terms: "wild food environments, " "natural food environment, " "river, " "food environment," "food security," "Mekong River, " "Cambodia, " "food environment, " "sustainable," "river food ecology, " "low middle income countries. " We specifically looked for studies that discuss rivers as food environments or discuss wild food environments in riparian populations, as well as literature on the dependence on the Mekong River (and other rivers) as a

Individual factors
Note: We adapted a schematic socioecological model of food environments 13 to reflect riverine food environments.

Policy & practice
Riverine environments and food security, Cambodia Swetha Manohar et al.
direct source of food in low-and middleincome countries. While the table is not exhaustive, its relevance is supported by the evidence reviewed to help expound factors captured and depicted in the conceptual framework in a way that is illustrative. 5,10,13,[17][18][19] The identification, organization and assessment of this information serve to bolster research and policy considerations on river systems as unique food environments. Food environments can be characterized as built or natural, the latter comprising both cultivated and wild food environments. Cultivated natural food environments make a significant contribution to the diets of subsistence farmers and rural communities through the production of staple crops, supplemental gardens that produce fruits and vegetables, and the rearing of livestock and aquaculture, and utilization of their by-products, such as eggs and milk. Cultivated food environments are often dependent and intrinsically linked with wild natural food environments, which include forests, jungles, rivers and lakes. These environments are particularly important for increasing access to nutrientrich foods, including animal source foods, leafy greens and other vegetables and fruits, 19 and can increase resilience of households to shocks. 20,21 Rivers act as wild food environments from which food (fish and edible aquatic plants) is procured, 22 but also as cultivated food environments where staple crops are grown. The riverbanks can serve as informal built food environments (habitual wet markets and mobile fish vendors) as well as formal built food environments where restaurants are situated. But river bodies also serve as a space for selling foods and allow for trade and transportation of food. As such, they cut across the different food environment types and the food system itself. From a public health policy standpoint, understanding the dynamic role of rivers as food environments is critically important in determining where, when and how to act to not only protect food security and diets, but to instil resilience of the rivers themselves as important food sources.

The case study
The Mekong River traverses south-east Asia and is shared by six countries -Cambodia, China, Lao People's Democratic Republic, Myanmar, Thailand and Viet Nam -where approximately Riverine environments and food security, Cambodia Swetha Manohar et al.
65 million people live in its basin. 23 In Cambodia, the river splits the country, flowing over 500 km, and comprises 39 river basins. Nearly 80% of the country's 16.7 million people rely on the basin for their livelihoods and other resources. 23 The Mekong River connects with the Tonle Sap Lake which, with its unique flood pulse hydrology, functions as the largest inland fishery in the world. 17 Currently, Cambodia's food systems are transitioning -they are expanding and transforming, moving away from smallholder self-sufficiency agriculture to more significant commercial production. However, with 75% (12.7 million) of the Cambodian population still living in rural areas, the Mekong River and its tributaries remain crucial to ensuring the country's food security.
The downstream impacts of hydropower dam construction on the Mekong River include altered water and sediment flow to the delta. 24 The alterations to the biophysical and hydrological system have significant effects on agricultural and fishery production, particularly for small-scale operators who are already constrained by the lack of resources and political agency, and threaten their livelihoods and agricultural ways of life. 24 The Mekong River Commission, established in 1995, provides a framework to promote cooperation in the region, including through data collection to facilitate river management. 25 However, the commission is limited in its capacity due to the lack of membership of key upstream countries, including China, and the mode of cooperation is not legally binding. Thus, governments may ignore the commission's recommendations if they impede governmental plans. For example, not all Mekong River Commissions' member states have been transparent about dam development. 26 Further, other regional cooperation agreements, such as the frameworks of the Mekong-Lancang Cooperation and Mekong-Republic of Korea Cooperation, are at times at odds with the commission and undermine its efforts. 25

Applying the framework
We expand our evaluation of the Mekong River as a food environment, starting at the band of food environments itself (Fig. 1), and discuss its interaction with individual factors and the diets of the Cambodian population. As described earlier, the river functions as a wild, cultivated and informal built food environment. Total fisheries production is estimated at 9.5 million metric tonnes of fish in 2018 which include capture fisheries and aquaculture products. 27 These yields support an average annual consumption of approximately 63 kg/capita in Cambodia in contrast to 20 kg/capita worldwide. 28 The distinctive flood pulse system of the Mekong River and Tonle Sap Lake is responsible for production of three quarters of the country's dominant agricultural product, rice. 29 Wild foods frequently harvested for consumption include snails, frogs, prawns, crabs, insects, waterbirds and aquatic plants. 30 The proportion to which river wild foods contribute to the overall caloric and nutrient intake of the Cambodian population is not well characterized, however, an estimated >90% of household catch of aquatic plants and animals (besides fish) is consumed by household members. 30 Beyond cultivation, the sale of food harvested from the river along with other types of food items (including processed foods) are sold on and around the river in both informal and formal markets.
Individual factors that interact with both the river as a food environment and dietary intake include values and beliefs, income, social capital, health, knowledge, skills and time. Cultural practices and celebrations, including the Water Festival and other religious customs, reflect belief and value systems at the individual and broader community level.
The reliance of the rural Cambodian population on the Mekong River for their livelihood and food security is high: approximately 80% of river communities directly rely on the river and lake for food and livelihoods and 45% of its households undertake fishing-related income activities. 31 Increasingly, Tonle Sap Lake communities have experienced reductions in catch quantity due to overfishing and ecological threats, but have limited access to resources for adapting to the situation. 32 Opportunities exist to assess the sustainability attributes of riverine food environments that reflect adaptive practices to climate and livelihood changes. Other individual factors include social capital; the links between social capital and food security are well-established, 33 but there is limited evidence in the Cambodian context. Of note, low accessibility to both social and human assets among lower Mekong River communities has impeded livelihood strategies, which has resulted in social incoherence. 34 Globally, maternal education is positively associated with both the mother's own and her child's dietary intake, a relationship that can be modified with food availability. 35 Time allocation, especially women's time and restrictions placed on their time, have been associated with poor child feeding practices and the mother's own quality of diet. 36 In recent decades, the dramatic increase in migration of women from rural areas to cities has affected both women's and children's diets. Ultimately, these individual factors can shape Cambodian diets, which are usually comprised of rice and fish as a primary protein source, both of which are river dependent. White fish (trey riel) commonly used to make fish paste (prahok) creates an affordable animal protein with a longer shelf life. These interactions of individual factors with riverine food environments to support food acquisition are important in a context where the burden of malnutrition and food insecurity is high. 37 For example, in 2021, during the coronavirus disease 2019 pandemic, estimates of household food security revealed that 32% of households experienced moderate and/or severe food insecurity, with the poorest households carrying a disproportionate burden. Among the poorest households, an estimated 55% experienced such food insecurity. 38 When considering the more distal layers of the conceptual framework, the literature shows evidence of different contextual factors in Cambodia influencing the Mekong River and its tributaries as a food environment. Sectors of influence, given their relationship with the Mekong River, are the agricultural, labour, markets, distribution, industry and technology sectors in Cambodia. Rice farming and fisheries livelihoods have been critical contributors to gross domestic product growth since the 1990s. 39 The sociocultural and, especially, the political environment of the Mekong River, is complex. There are currently an estimated 132 hydropower dams built, under construction or planned on the tributaries of the lower Mekong River. rectly affected water levels by restricting water flow, removing the anticipated seasonality of the rise and fall of water levels and blocking fish from upstream movement and sediment flow. 24,41 Projected production loss alone on capture fisheries in Cambodia is between 40% and 57% by 2030. 28 This loss would imply anywhere between 6.4 million and 21.1 million people losing their main protein source. 28 Without reliable river flows, seasonal food insecurity and a decline in agricultural productivity can affect an estimated 70% of inhabitants of river communities that rely on the river for fisheries livelihoods and food cultivation. 40 Conflict over water rights, illegal fishing practices and inconsistent regional cooperation are the major challenges in the transboundary Mekong River basin governance. 42 Finally, the river ecosystem comprises factors that reflect biotic, abiotic, climate, flow and habitat features of this ecosystem. Climate change is altering the Mekong ecosystem in various ways including its hydro-ecological conditions, sediment and nutrient flux, and vegetation growth 43,44 as well as the ability to harvest and grow food in and around the Mekong River. 45 Extreme droughts and floods have devastating consequences on the ecology of the river with future scenarios projecting increased risks of both. 46,47 Human activities in and along the river have affected flow dynamics, while significant increases in populations living in the lower Mekong area has put pressure on natural resources in the region. A shift has begun, moving away from smallholder farming towards more industrialized, specialized agriculture and cash crop systems, and farmers moving towards off-farm livelihoods. 48 Geophysical and anthropogenic forces have altered the agro-ecological landscapes of the basin, which has seen increasing deforestation due to forest-cover change and land-use conversion from forests to farmland. 49 Unsustainable agricultural practices have also been linked to dramatic habitat loss over the past 10 years (2300 km 2 of seasonally flooded habitat was lost to agriculture, with another

Natural food environment (rivers)
Attributes of quality  50 In addition, Cambodia faces the highest forest loss and deforestation rates among all countries in the Mekong basin, due to illegal logging, with significant negative impacts on floodplain productivity. 49

Assessing river food environments
Policy-makers need new tools to understand how riverine food environments are changing, the impacts on food security and diets, and how and where to intervene in the context of climate change. The framework in Fig. 2 illustrates the types of interdisciplinary assessments that exist to evaluate riverine food environments. 10,13 We highlight the six main attributes of food environments typically used for food environment assessment: (i) availability; (ii) affordability; (iii) convenience; (iv) promotion; (v) quality; and (vi) sustainability, and illustrate the corresponding measurements. 3,13,21,51 While tools may exist to assess certain (not all) attributes, these assessments have not been conducted in a holistic manner for riverine food environments. 13 This lack of assessment may relate to the complexity and breadth of such assessments. Given the uniqueness of riverine food environments, their assessment requires a multitude of tools from various disciplines not limited to ecology, hydrology, economics, food science, public health and nutrition. These attributes are influenced by macrolevel factors (Fig. 1) and river ecosystems themselves that respond to climatic change and other stressors. Understanding the availability, quality, affordability, convenience, promotion, and sustainability attributes of food environments (Fig. 2) can help public health policymakers and practitioners in developing, prioritizing and implementing localized policies. Such policies can improve those attributes to promote healthy and sustainable dietary choices and options for populations. For example, the attributes of quality shows how biodiversity is crucial for rivers to be fully functional food environments. Public health policy-makers can inform and collaborate with agriculture and fisheries ministries to ensure biodiversity of rivers; this protection and promotion of biodiversity can positively affect health. The dynamic nature of these riverine food environments adds an additional challenge in that they are kinetic, they change markedly based on the season and they are heavily influenced by climate variability and change. 13,19,42 This variability makes measuring aspects of sustainability and temporal features of these environments even more critical. Fig. 1 and Fig. 2 recognize the relationships, effects and trade-offs across the full riverine food environment system, and all the domains and dimensions of those relationships. Without a clear framing of those relationships and a conceptual understanding of where to intervene, it is challenging to account for the system dynamics and complexities and act across a range of policy interventions. Despite the existence of many food system frameworks for policy-makers, very few have incorporated ecosystems into them, and even fewer incorporate the role of rivers, which are crucial ecosystems for food security. 31 The application of the frameworks presented here allows for an approach to monitoring rivers and advocating their protection, management and utilization with greater purpose for food security and nutritional well-being. Further policy implications include paying greater attention to the downstream effects of energy planning including the pathways by which dam construction and land use decisions alter hydrology and drive food insecurity across borders and jurisdictions.

Conclusion
If we are to understand how to produce, acquire and consume food within planetary boundaries to support nutritional well-being, we cannot do so without characterizing and protecting ecosystems-based food environments that serve as a critical interface for food acquisition within larger systems. Rivers contribute in multiple ways to food security, diets and nutrition outcomes. In some areas of the world, such as the Mekong River basin, rivers are critical for food security and the livelihoods of millions of people.